This invention relates to the production of magnesium chloride. More particularly it relates to the production of magnesium chloride utilizing a refractory liner highly resistant to deterioration by reactants in the process.
It is known to produce magnesium chloride by the chlorination of magnesium oxide or an impure mixture of magnesium chloride and magnesium oxide by chlorinating the oxide in the presence of a reducing agent such as carbon or the like. For example, British patent specification No. 886,212 teaches the chlorination of a mixture of magnesium chloride and magnesium oxide by chlorinating a molten mixture of magnesium oxide and magnesium chloride while passing the materials through a carbonaceous material such as lump coal or coke or the like. However, such processes are normally carried out at elevated temperatures, for example the aforesaid British patent mentions the temperature of the chlorinator as 750.degree. to 900.degree. C. At this temperature, problems can arise with respect to the types of materials, particularly refractories, used in the apparatus from the standpoint of purity of the magnesium chloride and magnesium produced therefrom. Also, serious problems can arise if the refractories used are not resistant to attack by molten magnesium chloride in the chlorinator, for example, or gases emanating therefrom such as chlorine, phosgene, carbon tetrachloride and boron trichloride. For example, British patent specification No. 149,670 describes a process for producing magnesium chloride using carbon tetrachloride, oxychloride of carbon or phosgene, i.e., using carbonated chloride to provide a reaction temperature of about 500.degree. to 600.degree. C. The patentee states the low reaction temperature of 500.degree. to 600.degree. C brings the advantage that the question regarding the apparatus is not difficult to solve. However, because of advantages of operating at the higher temperature, it is desirable to provide a system wherein magnesium chloride could be formed by the chlorination of magnesium oxide with chlorine in the presence of a reducing agent wherein the reaction vessel is substantially impervious to attack from the reactants. Similarly, it is desirable to provide also a refractory for use in an electrolytic cell for the decomposition of the magnesium chloride to form magnesium which is resistant to attack by the electrolyte, molten magnesium and gases evolved during the decomposition process. Having a refractory resistant to attack avoids frequent shutdown of the cell for repair purposes and prevents contamination of the magnesium produced.